A new study from researchers at C.C.N.Y. (City College of New York) examined the connection between improvements in posttraumatic stress and improvement in substance abuse over the course of time in 353 women diagnosed with both conditions.

Participants were randomly assigned to 12 sessions of either trauma-focused treatment or health education. Assessments were made on the PTS and the substance use during treatment at 1 week and posttreatment after 3, 6, and 12 months.

Subjects showing no improvement, an improvement in the substance use
only, or a total, global improvement early on, tended to maintain their
original diagnosis over time; but subjects initially exhibiting
improvement in their PTSD symptoms were significantly more likely to
transition into a global response over time, indicating that they
maintained their PTSD improvement, and that it was associated with
subsequent improvements in substance use.

Additionally, trauma-focused treatment was significantly more effective than the health education method in achieving substance use improvement, but only among those who were heavy substance users at baseline and had achieved significant PTSD reductions.

This study concludes that reductions in PTSD severity were more likely to be associated with substance use improvement, but that it did not work the other way around: reductions in substance abuse did not lead to improved PTSD symptoms. These results support the self-medication model of coping with PTSD symptoms, and an empirical basis for integrated interventions for improved substance use outcomes in patients with severe symptoms.